RFR (s) 8057846: ClassVerifier::change_sig_to_verificationType temporary symbol creation code is, hot

[Coleen Phillimore]

Summary: Only update the refcount without looking it up in the symbol table.

open webrev at http://cr.openjdk.java.net/~coleenp/8057846/
bug link https://bugs.openjdk.java.net/browse/JDK-8057846

Ran regression tests (testbase, runtime jtreg).  Aleksey verified 
performance improvement.

Thanks,
Coleen